Exhaust gas cooler for an internal combustion engine

ABSTRACT

An exhaust cooler for a combustion motor is provided that includes a flow path for guidance of the exhaust from a combustion motor, wherein the flow path has a wall to separate the exhaust gas flow from a cooling fluid and wherein heat is exchangeable via the wall between the exhaust and the cooling fluid, wherein the wall is covered at least partially by a flexible thermoelectric film.

This nonprovisional application is a continuation of International Application No. PCT/EP2009/066507, which was filed on Dec. 7, 2009, and which claims priority to German Patent Application No. DE 10 2008 063 701.7, which was filed in Germany on Dec. 19, 2008, and which are both herein incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an exhaust gas cooler for an internal combustion engine.

2. Description of the Background Art

Fundamental discussions have addressed the use of the exhaust gas of internal combustion engines to operate thermoelectric elements such as Seebeck elements. The overall efficiency of the internal combustion engine can be improved as a result. Solutions that can be applied in series production have been hindered by, inter alia, the costs and structural complexity of available thermoelectric elements.

DE 10 2006 055 120 A1, which corresponds to U.S. 20080121263, which is incorporated herein by reference, and which describes a thermoelectric foil that withstands high temperatures due to the properties thereof, and has sufficient mechanical flexibility for application onto curved or angled surfaces. A thermoelectric foil in the sense of the present invention can be a foil as illustrated in DE 10 2006 055 120 A1. In suitable embodiments at least, the foil has sufficient temperature resistance for operation using hot exhaust gas as the heat source.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide an exhaust gas cooler for an internal combustion engine, which can be used to convert the thermal energy of the exhaust gas, in part, into a more valuable form of energy.

This problem is solved according to an embodiment of the invention for a heat exchanger, by covering a wall with a flexible thermoelectric foil, a thermoelectric element having a large surface area can be disposed in the exhaust-gas flow of the engine in a low-cost and effective manner. Since the exhaust gas cooler is regularly provided anyway for other reasons, such as to recirculate exhaust gas to reduce emissions, hardly any additional design changes are required, except for providing the foil and possibly also control electronics to supply the current withdrawn therefrom to a vehicle electrical system, for instance. In such an exhaust gas cooler, the exhaust gas also flows across a particularly large surface or wall of the flow duct, thereby making it possible to generate high electric power. Furthermore, the cooling fluid represents a powerful and defined heat sink for the thermoelectric element.

In an embodiment of the invention, the fluid is a liquid coolant of a coolant circuit, thereby ensuring that the local temperature difference is particularly great and the thermal capacity is great.

In an embodiment of the invention, the exhaust gas cooler is in the form of a bundle heat exchanger, wherein each wall is designed as a wall of one of a plurality of exchanger tubes. In an alternative embodiment of the invention, the exhaust gas cooler is in the form of a plate heat exchanger, wherein each wall is designed as a surface of a stacked plate of the heat exchanger. In the case of exchanger tubes and in the case of stacked plates, the flexible thermoelectric foil can be applied easily and reliably to the heat-conveying surfaces and to the wall disposed between the exhaust gas and the cooling fluid.

In an embodiment, the thermoelectric foil is applied to the wall at least on the exhaust-gas side. As a result, a particularly great temperature difference between the opposite surfaces of the foil and, therefore, particularly high efficiency, can be attained.

Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWING

The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein the sole figure shows a partial side view of an exhaust gas cooler according to the invention.

DETAILED DESCRIPTION

The exhaust gas cooler shown in the figure is in the form of a bundle heat exchanger, in which a plurality of parallel exchanger tubes 1—each of which forms a flow path 1 a—are disposed in a housing or water jacket 3 through which coolant flows. Exhaust gas from an internal combustion engine of a motor vehicle flows through exchanger tubes 1 in order to transfer heat from the exhaust gas to the coolant through the walls of exchanger tubes 1. The cooled exhaust gas is then supplied at least in part to the inlet side of the internal combustion engine, e.g. to reduce the emission of nitrogen oxides in the case of diesel engines.

A flexible thermoelectric foil 2 is applied to the inner side of exchanger tubes 1, on the exhaust-gas side. Foil 2 therefore has the best possible thermal contact with the wall of the exchanger tube. Depending on the design of the foil, the contact can be thermally and mechanically configured, e.g. by flat soldering.

The foils are electrically contacted at intended contact points (not depicted), thereby enabling electrical energy to be withdrawn therefrom during operation of the exhaust gas cooler. This energy can be supplied to an electric circuit of the motor vehicle, for which purpose appropriate control electronics may be provided.

Depending on the requirements, a plurality of foils can also be disposed one above the other and, alternatively or in addition thereto, a foil can be provided on the coolant side of the exchanger tubes.

The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims. 

1. An exhaust gas cooler for an internal combustion engine, comprising: a flow path configured to guide exhaust gas from an internal combustion engine; a wall arranged in the flow path for separating the exhaust gas flow from a cooling fluid, wherein heat is exchangeable between the exhaust gas and the cooling fluid via the wall; and a flexible thermoelectric foil arranged such that the thermoelectric foil at least partially covers the wall.
 2. The exhaust gas cooler according to claim 1, wherein the fluid is a liquid coolant of a coolant circuit.
 3. The exhaust gas cooler according to claim 1, wherein the exhaust gas cooler is in the form of a bundle heat exchanger, wherein each wall is designed as a wall of one of a plurality of exchanger tubes.
 4. The exhaust gas cooler according to claim 1, wherein the exhaust gas cooler is in the form of a plate heat exchanger, wherein each wall is designed as the surface of a plate stack of the heat exchanger.
 5. The exhaust gas cooler according to claim 1, wherein the thermoelectric foil is applied to the wall at least on the exhaust-gas side. 